The invention relates to a method of automatic handling of phone numbers which are stored in an electronic phone list contained in a portable phone which is connected to a cellular network and one or more cordless networks.
The use of cellular phone systems creates problems, as numbers which may be called by a portable phone, have different formats according to whether the portable phone is present in the same region, in the same country or in another country relative to a phone which is being called. This problem has been solved in the GSM network by allowing it to analyse a called phone number and determine the correct format. This requires that the called phone number is in a so-called international format initiated by a "+" followed by a country code, which is "49" for Germany. This is followed by the number which would have to be called in an international call, which means that regional escape codes are omitted. The GSM network itself is capable of adding the necessary escape codes to the number--both internationally and regionally.
This functions excellently as far as it goes, but it must be expected in future that portable phones may be connected to both cellular networks, such as GSM, and cordless networks, such as DECT, thereby operating as dual mode phones. In DECT systems, the internal numbers will typically be extension numbers to a main number in a PSTN system. The dual mode phone will therefore be capable of calling a phone having an international type phone number via the cellular network, and a short extension number via the cordless network. If the phone number concerned is stored in the electronic phone number register or phone list of the dual mode phone, it must be stored in the long international format as well as in the extension number format, and the user himself must select the correct format when calling. A wrong selection here will have as a consequence that the cordless part of the phone cannot establish a call if it has the PSTN number as its input, or that the cellular part of the phone establishes a cellular call at a cellular rate, even though the in-house cordless rate is considerably cheaper.